Method of polymerizing trifluorochloroethylene



Jan. 20, 1953 w. T. MILLER ET AL 2,626,254

METHOD OF' POLYMERIZING TRIFLUOROCHLOROETHYLENE Filed Nov. 29. 1948 Patented Jan. 20, 1953 METHOD OF POLYMERIZING TRIFLUORO- CHLOROETHYLENE William T. Miller, Ithaca, N. Y., and John T. Maynard, Wilmington, Del., assignors to the United States of America as represented by the. United States Atomic Energy Commission Application November 29, 1948, Serial No. 62,592

11 claims. (011260-921) This invention relates to a method of preparing halogen containing polymers and more particularly to a method of preparing polymers consisting essentially of carbon and halogen with a high iluorine content. i

In recent years polymers consisting substantially of carbon and halogen with a high percentage of fluorine, because of their high degree of inertness, have come to be of great interest for various applications in industries in which corrosive substances are used. The plastics, which are polymers of this type having substantial mechanical strength, are ofparticular interest as materials of construction in these industries.

One very useful method of preparing the plastics is to carry out the polymerization of a suitable olen in the presence of a halogen substituted acetyl peroxide as a polymerization promoter. The mechanism of the polymerization is such that the promoter decomposes, forming free radicals, and occasionally fragments of the promoter enter the polymeric chains. An advantage of this type of process is that the halogen substituted acetyl peroxides contribute little hydrogen to the products, which hydrogen tends to decrease their inertness; and this is particularly true of the completely halogen substituted acetyl peroxides which contribute no hydrogen. It has been found that when the polymerization is carried out at relatively low temperatures, plastics of higher molecular weight are produced; and that relatively low temperature polymerization can be carried out employing the completely halogen substituted acetyl peroxides which are active at these low temperatures. Thus, the latter peroxides are active and decompose already at about room temperature. Also, they are sensitive to shock and sometimes decompose with explosive violence. Therefore, in the purification, handling and storage of these peroxides it is necessary that they be maintained at a temperature below about 0 C., and it is desirable that they be kept in the form of a dilute solution in a halogenated organic solvent such as trichloro- 'iluoromethane Such precautionary measures are in some cases difficult to carry out, and tend to increase the cost of the process.

It is therefore an important object of the invention to provide a more convenient and eco- According to the invention, a compound se-vl lected from the group'of completely halogen sube stituted acetyl halides and completely halogen substituted acetic acid anhydrides is caused to react with an inorganic peroxide to form the corresponding substituted acetyl peroxide, in situ in a polyfluorinated olen consisting of carbonand halogen of -at least 2 and preferably of 2 to 4 carbon atoms; and then the olefin is polymerized in the presence of the thus produced organic peroxideas a polymerization promoter. It has been found that the formation of. the organic peroxide in situ and the polymerization may be made to take place in a-single operation, that is, under the same conditions, particularly tempera-j ture. Further, it has beenfound that formation of the peroxide takes place at temperatures b,e low the temperatures at which it decomposes and promotes polymerization at an effective rate. `It ispreferred tomaintain the reaction -mixture irst at a relatively low temperature at which the lperoxide vforms yand at which its decomposition is very.4V slow, the -former reaction being allowed to progress until a desired concentration of the peroxide in theolen is built up; and thereafter Warm the reaction mass to a temperature v at which the peroxide decomposes at a moderate; useful rate and promotes polymerization. Using thistwo stage process, high yields of polymer having useful propertiesy as rplastics havelbeen obtained. In addition, this process permits, be-l tween the step of forming the peroxide promoter andthe step of polymerization, ltering the re- -action mass to remove substances such as inor ganicperoxides or oxides whereby products of greater purity may subsequently be obtained.

, .The concentration of the organic peroxide may be determined prior to polymerization and rmay be brought toauesired vaine.Y Relatively low concentrations of the` peroxide tend vto produce polymers of relatively high molecular weight, and vice versa, so that reproducibility of theproducts depends to some extent on reproducibility of the peroxide concentration. Hence the two stage process is of value with respect to control of the products. t 1

The temperature at which polymerization should be carried out depends on the particular organic peroxidek that is formed in situ. The criterion is that the temperature should'be .with-A in a range in which the peroxide decomposesat a moderate,`regulated non-violent rate and is an active polymerization promoter. The temperature range will vary among the individual per,-` oxide promoters. Formation of the promoter in A situ maybe carried out under the same'conditions or alternatively may be carried out at relatively lower temperatures at which its decomposition is very slow, resulting in the benefits described above. In general, the completely halogen substituted acetyl peroxides are active already at 'about room temperature. vIn the case of trichloroacetyl peroxide, a useful temperature range for carrying out both reactions is 25 C. to C. and better 20 C. to 0 C. but it is preferred to maintain the reaction mixture 'at a temperature below 25 C. to form the peroxide in desired concentration, and thereafter Warm the reaction mass toa temperature between 25 C. and 10 C. and better between 20 C. and 0 C. and bring about polymerization. It has been found that the concentration of the peroxide promoter reaches a maximum in 3 to 6 hours so that the lowest temperature stage of theprocess is completed in a short time. In comparison, ,longerperlods of very low temperature refrigeration are Vneeded to prevent the decomposition of the peroxide when it is separately prepared and 'stored for use as required.

.Ithas been foundthat preparation of the promoter inV situ in the olefin is feasible and does not interfere with the polymerization. The olen is capable of servingas a solvent for the substituted acetyl halide ior anhydride thus facilita'ting reaction. Simple ltration, extraction and washing procedures may vbe used to obtain the products `"in a useful, purestate.

The term inorganic peroxide vis used herein in the narrow sense to signify an 'inorganic compound in which two oxygen atoms are connected by-a single bond. The inorganic peroxides comprise hydrogen peroxide, the alkali metal peroxides ,and the alkaline earth metal peroxides.

In the following description, one property of the polymers designated the N. S. T., or no strength temperature, which provides an indication of relative molecular weight, will be referred to. vThe N. S. T..may be measured by-a procedure .set forth in application Serial No. 730,176, filed February 21, 1947,'by W. T. Miller. As described in that application, in measuring N. :SJ-T. aspeciic apparatus is used as illustrated in the drawings wherein:

Figure 1 isan elevation of an N. S. T. measuring apparatus with the heating unit in Vertical Section.

.Figure2 is a detail view of the rtestsample and sampleclamp, the clamp being vpartly'shown in axial section.

Figurev 3 is adetail `view-of the test sample.

As .shown in Figs. 1 land 2 Vthe sample 2 is clamped between .the jaws 3 of .the clamp I by tightening the set .screw 4. The clamp I is an extension Vof the .plug VII which is inserted into the bore Iof the tube I3. vThe plug II serves to center the sample .2 in the bore I4 of .the tube I3 :and vthe flange I2 limitsthe extent to which the-,plug .may be inserted in the bore. The tube I.3 `isheated by electrical heating element I5. The temperature of the heating element is controlled .by .a Vresistance I6. The temperature of the ,block is measured .by a thermometer 2| in thermometer well .I'|. The apparatus is thermally insulated by the insulating members I8 and I9 Aand member I8 can be removed to give access to the plug II. A weight '20 is attached tosample 2 by a free hanging Wire 8 which passes through the insulation .I9 at hole 22. VA scale 2.3 serves to indicate the movement of the Vweight 20. The testis performed byiclamping Va sample of specified dimensions of polymer into the clamp as shown in Figure 2, placing it in the heater in the position shown in Figure 1, and heating it slowly until it breaks. The dimensions of each sample must be reproduced to careful specifications. The sample 2 is notched at the center 6 to insure its breaking at this point.

A sample of polymer hot pressed into a 1% thick sheet, is cut into a strip 1/8" by e" by 2 and vnotched as indicated in Figs. 2 and 3 to a thickness of 3%,14 by ils at notch 6. A ne wire 8 and weight '23 are attached to the lower end at the notch l so .that the total weight from the notch `i'i down is 0.5 gram. The temperature of .the sample is increased at the rate of about 1.5 'C. per minute las Vthe breaking temperature is 'approached b y slowly increasing the potential across the heating element I5.

lThe-method of the invention is illustrated by the following examples:

Example 2 A glass bomb was charged with about 42 gs. triiiuoromonochloroethylene, 6 gs. 88% BaO2 and l cc. CClaCOCl, and maintained at 20 C. for 8 days. vAfter extraction with hot C014 and drying, a yield of 19% of plastic polytrifluoromonochloroethylene was obtained.

Example 3 A mixture of '7 jgs. CCl3COCl, 250 ccs. CF2=CFCl and 70 gs. BaOz was stirred for 7-1/2 .hours .at 30 C., ltered and transferred to glass tubes. The tubes were maintained at 0 C. for 10 days. On workingup the products, a yield of about 65% of polytriluoromonochloroethylene, N. S. T. about 220 C., was obtained.

Example. 4

A mixture of 300 c cs. VC`E'2=,CFC1, 10 gs. CClsCOCl and 4.6 gs. sodium peroxide (NazOz) was stirred at 30 C. yAt intervals, samples of the reaction mixture were removed and filtered and analyzed for bistricholoroacetyl peroxide. content. This was done byiadding to the sample a solution of ethyl alcohol, glacial acetic acid and potassium iodide and titi-ating with a standard sodium thicsulfate solution; and the followingresults were obtained:

Weight Percent Time (his.) (COISCOz)2 At the end of this time samples were filtered and transferred to individual glass tubes and were treated in the following manner.

Sample No. 1 was maintained at 0 C. for about 11/2 days. After extraction of impurities with hot C014 an y8% yield of polytriuoromonochloroethylene, N. S. T. 271 C., was obtained.

acogen "y `Sample No. 2 was maintained for 3 days at a 'temperature which varied between 0 C. and 10 Example 5f The samereactants were mixed as set forth in Example '4, with the exception that the quantities lof CClsCOCl and of NazOz'were tripled. The vreactants were stirred at 30 C. for 541/2 hours after which time the trichloroacetyl peroxideconf tentmeasured- .189% by weight. Samples were .o

illtered andtransferred to glass tubes and treated i in the following manner.

Sample No. 1 was maintained at 0 C. for nearly all of 21/2 days except that it was warmed to 10 C.

for the last few hours. After extraction polytriiluoromonochloroethylene, N. S, T. 232 C. in 30% yield, was obtained.

Sample No. 2 was held at 20 C. for about 1 day and was then allowed to warm slowly to room temperature. Polytriuoromonochloroethylene was obtained in 27% yield.

The method `of the present invention is particularly useful when applied to polyiiuorinated olens consisting of carbon and halogen of 2 to 4 carbon atoms and'when completely halogen substituted-acetyl halides or -acetic acid anhydrides are used. Other examples of such oleiins are tetrafiuoroethylene, hexafiuorobutadiene 1,3, hexauoro propene, asymmetric diiluorodi'chloroethylene and mixtures suchas a mixture of tetrafluoroethylene and trifluoromonochloroethylene and a mixture of triiluioromonochloroethylenerand hexafiuoropropene. Other examples of the acetyl compound are dichloroluoroacetyl chloride and triiiuoroacetic anhydride. However, the invention is also applicable to other completely halogenated olens and to other halogenated olens of 2 to 4 carbon atoms such as vinyl chloride and asymmetric dichloroethylene, and other halogen substituted-a-cetyl halides or -acetic acid anhydrides may be used such as monoand di-chloroacetyl chloride and diiluoroacetyl chloride.

The process of this invention may be employed to prepare vnormally liquid polymers as well' as normallyrsolid polymers without departing yfrom the scope thereof. The process may be carried out in either a batchwise or continuous manner. In producing polymer oils, a continuous process is particularly feasible. For example, the vhalo-v gen substituted acetyl halide or acetic acid anhydride may be admixed with and dissolved in the monomer. The resulting mixture is continuously passed through a rst reaction zone in the presence of an inorganic peroxide. The inorganic peroxide may be in situ in the reaction zone or continuously added thereto in the desired proportions. The temperature conditions maintained in the reaction zone are relatively low but favorable to the formation of the organic per--` oxide. A liquid effluent comprising monomer and organic peroxide is removed from the reaction zone and passed to a second reaction zone maintained at a higher temperature favorable to the polymerization of the monomer to oils. An oil comprising the polymer product is continuously withdrawn from the second reaction zone. For a 6 more detailed discussion of the conditions of reacl tion in the polymer oil production, reference may be had to application Serial No. 743,455, William T. Miller, led'April 23, 1947.

l By means of the present invention a convenient and inexpensive method of preparing useful plastic materials is provided. Since many embodiments might bernadeof the present invention and since many changes mightl be ymade in the embodiment described, it is to be understood that the foregoing description is to be interpreted as illustrative only and not in a limiting sense.

We claim.:

--'1. Tlie method of preparing polytrifluoromonochloroethylene which comprises maintaining a compound selected fromv the group consisting of completely halogen substituted acetyl halides and completely halogen substituted acetic acid anhydrides, said halogen being selected from the group consisting of fluorine and chlorine, which is in solution in 'trifluoromonochloroethylene, in contact with an inorganic metal peroxide, to produce the peroxide of said compound in situ, and decomposing the peroxide so formed by maintaining the same at a temperature at which it decomposes while still in contact with said trifluoromonochloroethylene, thereby causing the latter to polymerize. A v

2. The method of preparing polytrifluoromonochloroethylene which comprises maintaining trichloroacetyl chloride in contact with an inorganic metal peroxide in situ in trici-lucromonochloroethylene to produce bis-trichloroacetyl peroxide and maintaining the reaction mass at a temperature to decompose the peroxide so formed while still in contact with said triiluoromonochloroethylene thereby causing said trifluoromonochloroethylene to polymerize forming a solid polymer. Y

3. The method of preparing polytriiiuoromonochloroethylene which comprises maintainingtrichloroacetyl chloride in contact with barium peroxide in situ in triiluoromonochloroethylene to produce bis-trichloroacetyl peroxide and maintaining the reaction mass at a temperature to decompose the peroxide so formed while still in contact with said trifluoromonochloroethylene thereby causing said triuoromonochloroethylene to polymerize forming a solid polymer.

4. The method of preparing polytriuoromonochloroethylene which comprises maintaining trichloroacetyl chloride in contact with sodium peroxide in situ in trifiuoromonochloroethylene to produce bis-trichloroacetyl peroxide and maintaining the reaction mass at a temperature to decompose the peroxide so formed while still in contact with said triiluoromonochloroethylene thereby causing the trifluoromonochloroethylene to polymerize forming a solid polymer.

5. The method of preparing polytrifluoromonochloroethylene which comprises maintaining trichloroacetyl chloride in contact with an inorganic metal peroxide in situ in triiluoromonochloroethylene to produce bis-trichloroacetyl peroxide and maintaining the reaction mass at a temperature to decompose the peroxide so formed while still in contact with said triiluoromonochloroethylene thereby causing the trifluoromonochloroethylene to polymerize forming a solid polymer, the foregoing reaction steps being carried out at a temperature in the range of 25 C. to 10 C.

6. The method of preparing polytriuoromonochloroethylene which comprises vmaintaining trichloroacetyl chloride incontact with an inorganic :metal peroxide vin situ in trifluoromonochloroethylene to produce bis-trichloroacetyl peroxide and maintaining the reaction mass at a temperature to decompose the peroxide so formed while still in Contact with saidtriiiuoromonochloroethylene thereby causing the triuoromonochloroethylene to ypolymerize forming Aa solid polymer, the foregoing steps being carried-out at a'temperature in the range of 20o C. to C.

7. The method of preparing polytriuoromonochloroethylene which comprises maintaining trichloroacetyl chloride in -contact with an inorganic peroxide .at a relatively low temperature :in lsituin triuoromonochloroethylene to vbuild upa desired concentration of bis-trichloroacetyl peroxideand thereaftenraising the temperature of the reaction mass to decompose the latter peroxide at, a.moderate rate and cause the trifiuoromonochloroethylene to polymerize forming Aa solid polymer.

J8. The method of vpolymerizing trirluoromonochloroethylene which comprises maintaining trichloroacetyl chloride in contact with an inorganic peroxide at a temperature below' 25 C. 'in situ in triuoromonochloroethylene to build up a desired concentration of bis-trichloroacetyl peroxide and thereafter warming the reaction mass to a temperature between 25 C. and 10" C. to decompose .the latter peroxide and cause the triiiuoromonochloroethylene to polymerize forming a solid polymer.

9. The method of polymerizing trifluoromonochloroethylene which comprises maintaining trichloroacetyl chloride in Contact With an inorganic peroxide at a temperature below 25 C. in situ in triuoromonochloroethylene to build up a desired concentration of bis-trichloroacetyl peroxide and thereafter warming the reaction mass -toa temperature `between 20 C. and 0 C. to decompose the latter peroxide and cause the trifluoromonochloroethylene to polymerize forming asolid polymer.

1.0. lThe method of polymerizing triiiuoromonochloroethylene which comprises maintaining trichloroacetyl chloride in contact with an inorganic peroxide at a vtemperature of about 30 C. in situ in trifluoromonochloroethylene to build up a desired concentration of bis-trichloroacetyl peroxide and thereafter maintaining the reaction mass at a temperature between 20 C. and 0 C. to decompose the latter peroxide and cause the triiluoromonochloroethylene to polymerize forming a solid polymer.

11. 'Ihe method of polymerizing trifluoromonochloroethylene which comprises maintaining trichloroacetyl chloride in contact with an inorganic peroxide at a temperature below 25 C. in situ in triuoromonochloroethylene to build up a desired concentration-of bis-trichloroacetyl peroxide, and thereafter filtering the reaction mass and then warming the reaction mass to a temperature between 20 C. and 0 C. to decompose the latter peroxide and cause the trifluoromonochloroethylene to polymerize forming a solid polymer.

WILLIAM T. MILLER. JOHN T. MAYNARD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,333,633 Britton Nov. 9, 1943 2,490,800 Greenspan Dec. 13, 1949 2,531,134 Kropa Nov. 21, 1950 2,580,373 Zimmerman Dec. 25, 1951 OTHER REFERENCES Miller et al., Ind. Eng. Chem., 39, S33-337 (March 1947).

Whitmore: Organic Chemistry, page 295; Van Nostrand (1937). 

1. THE METHOD OF PREPARING POLYTRIFLUOROMONOCHLOROETHYLENE WHICH COMPRISES MAINTAINING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF COMPLETELY HALOGEN SUBSTITUTED ACETYL HALIDES AND COMPLETELY HALOGEN SUBSTITUTED ACETIC ACID ANHYDRIDES, SAID HALOGEN BEING SELECTED FROM THE GROUP CONSISTING OF FLUORINE AND CHLORINE, WHICH IS IN SOLUTION IN TRIFLUOROMONOCHLOROETHYLENE, IN CONTACT WITH AN INORGANIC METAL PEROXIDE, TO PRODUCE THE PEROXIDE OF SAID COMPOUND IN SITU, AND DECOMPOSING THE PERIOXIDE SO FORMED BY MAINTAINING THE SAME AT A TEMPERATURE AT WHICH IT DECOMPOSES WHILE STILL IN CONTACT WITH SAID TRIFLUOROMONOCHLOROETHYLENE, THEREBY CAUSING THE LATTER TO POLYMERIZE. 